Quick Dictionary is rated as most "Useful" English to English Dictionary available in play store.

Features that make it very useful are:
- Search meanings from any reading app very quickly.
- No need to open the dictionary app every time.
- Searched words get stored in a list for later learning.
- Take quiz among words in the list.
- Inbuilt wordlists for preparing for exams like GRE / GMAT / TOEFL.
- Works very quick offline.
- Narrations are also available for the words searched.
- Quickly search the web to get more info

Full Version Features:
- Save sentences as usage examples.
- Backup your wordlists.
- Share wordlists with friends in CSV format.

Overall its a best app for learning English and building vocabulary.